Battery bank cooling

[NeilTheCop]

I'm about to push the buy button on a couple of Battle Born 100Ah 12V LiFePo batteries. The spec sheet says they will shut down at 135F. Sounds a lot but here in south eastern New Mexico it can easily exceed that in a closed building, such as where I intend to put my batteries to keep the thieves at bay. I'm quite happy to put them inside the house; the wife, not so much. I thought of building an insulated box with some 12V Peltier modules but at only 5% efficiency it seems impractical.
So can I get some suggestions from the forum members on how to keep the batteries cool as excess heat is bad for all batteries no matter their chemistry?

[jflorey2]

So can I get some suggestions from the forum members on how to keep the batteries cool as excess heat is bad for all batteries no matter their chemistry?

Keeping batteries cool will extend their life. Peltier junctions are terrible. Keeping the box cool with a high efficiency A/C works, as does using a chiller on batteries that will take coolant (like Tesla modules.)

[Tecnodave]

NeilTheCop

There is a post on forum.solar-electric.com that details a water cooled bank of batteries in Nicaragua that is done with local materials, very cleverly done

https://forum.solar-electric.com/discussion/354578/water-tank-cooled-batteries-temperature-sensor-placement

[J.P.M.]

NeilTheCop

There is a post on forum.solar-electric.com that details a water cooled bank of batteries in Nicaragua that is done with local materials, very cleverly done


https://forum.solar-electric.com/dis...nsor-placement

Neil:

For the system shown, once safety concerns are addressed with respect to whether or not your batteries can be (partially or completely) submerged in water, the problem becomes one of first determining a heat load, then, how to meet it, how much of a PITA is tolerable, and how much it will cost.

While expedient and cheap, and as the text suggested, temporary, I'd suggest frozen water in a bottle is not a long term solution as a cooling source. For one thing, if a long term solution , it would be more efficient (but maybe impractical) to provide the cooling to the battery bank directly rather than use it to freeze water and then use the ice to cool the battery.

If the submerged battery system is determined to be safe, one thing to consider would be an evaporative (swamp) cooler type of setup, but unless you're in a windy environment, that would require electricity to run a fan, and it takes a fair amount of power to move a relatively small mass of air --->>> the battery bank may become undersized. On the other hand, low dew points common most of the year in NM, except maybe during monsoon season will work to your benefit.

Depending on the (thermal) mass of the batteries, one tool that can be a bit useful and is often overlooked is to utilize the thermal mass of the batteries as something of a thermal flywheel and ventilate the (security ?) enclosure at night when it's cooler, maybe with forced ventilation, but maybe not, depending on what the battery temps. look like in the morning. Then because the batteries are cool(er) after being exposed to cooler air at night, the enclosure is then buttoned up in the early A.M. The batteries will heat up during the day, but with good design, they'll stay below some max. temp. until things cool down later in the day. Then, open the enclosure at night and resume the cooling cycle. Kind of a PITA, but may need little or no power to operate.

One other possible expedient: And not entirely tongue in cheek, depending on the battery bank size, put the whole damn thing in a fridge and set the fridge thermostat as high as possible. Or, put a tank of water in the fridge and circulate the water around the batteries. A decent fridge might use 1-2 kWh/day or less, +/- some.

NOTE: Regardless of the cooling design method chosen, think safety first. I'd be very careful about, and pay very close attention to, any enclosure ventilation requirements and other battery safety considerations that might be in conflict with restricting air circulation to the battery bank for the purpose of keeping it cool.

[Tecnodave]

Neil,

Read down that thread, the ice in bottle was the proof of concept, it was replaced with a chiller which operated from solar input. There are also links to other threads in that post.

[NeilTheCop]

Neil:

For the system shown, once safety concerns are addressed with respect to whether or not your batteries can be (partially or completely) submerged in water, the problem becomes one of first determining a heat load, then, how to meet it, how much of a PITA is tolerable, and how much it will cost.

While expedient and cheap, and as the text suggested, temporary, I'd suggest frozen water in a bottle is not a long term solution as a cooling source. For one thing, if a long term solution , it would be more efficient (but maybe impractical) to provide the cooling to the battery bank directly rather than use it to freeze water and then use the ice to cool the battery.

If the submerged battery system is determined to be safe, one thing to consider would be an evaporative (swamp) cooler type of setup, but unless you're in a windy environment, that would require electricity to run a fan, and it takes a fair amount of power to move a relatively small mass of air --->>> the battery bank may become undersized. On the other hand, low dew points common most of the year in NM, except maybe during monsoon season will work to your benefit.

Depending on the (thermal) mass of the batteries, one tool that can be a bit useful and is often overlooked is to utilize the thermal mass of the batteries as something of a thermal flywheel and ventilate the (security ?) enclosure at night when it's cooler, maybe with forced ventilation, but maybe not, depending on what the battery temps. look like in the morning. Then because the batteries are cool(er) after being exposed to cooler air at night, the enclosure is then buttoned up in the early A.M. The batteries will heat up during the day, but with good design, they'll stay below some max. temp. until things cool down later in the day. Then, open the enclosure at night and resume the cooling cycle. Kind of a PITA, but may need little or no power to operate.

One other possible expedient: And not entirely tongue in cheek, depending on the battery bank size, put the whole damn thing in a fridge and set the fridge thermostat as high as possible. Or, put a tank of water in the fridge and circulate the water around the batteries. A decent fridge might use 1-2 kWh/day or less, +/- some.

NOTE: Regardless of the cooling design method chosen, think safety first. I'd be very careful about, and pay very close attention to, any enclosure ventilation requirements and other battery safety considerations that might be in conflict with restricting air circulation to the battery bank for the purpose of keeping it cool.

Not fond of the submerge in water idea. Saw too many old movies showing an electrical appliance kicked into a bathtub with the obvious end result.
But your tongue in cheek idea of a fridge got me thinking.
Around here we have no shortage of old inefficient and non working chest freezers big enough to hold half a cow being hauled to the local dump. So to start there's a nice big pre insulated sealed box with a lid. Then replace the old compressor with either a Danfoss 12 volt scroll or a small 120v compressor with it's own pure sine inverter (I have an old water cooler that leaks, so there's my donor compressor, and coils). Lead acid would need a venting system, possibly an Arduino controlled fan and triggered by a hydrogen sensor. The Arduino could also be used for the compressor control to keep the temperatures within a precise set range.
Thank you for planting the seed of an idea.

[Tecnodave]

NeilTheCop,

Read down that thread a bit there are two more links to threads in there that are interesting approaches to the problem. I would not worry about a low voltage battery bank immersed in water, not submerged, you need an inch on top, The Danfoss compressors use a totally different freon gas than older referigerator and that conversion would be difficult, however a water chiller unit is quite appropriate for such a use. Quite small, efficient compressor chiller setup.

Just throwing an idea at you. I agree that excessive heat is bad for batteries and those battle born guys are not cheap batteries, IMHO cooling them would be worth it.

David

[NeilTheCop]

NeilTheCop,

Read down that thread a bit there are two more links to threads in there that are interesting approaches to the problem. I would not worry about a low voltage battery bank immersed in water, not submerged, you need an inch on top, The Danfoss compressors use a totally different freon gas than older referigerator and that conversion would be difficult, however a water chiller unit is quite appropriate for such a use. Quite small, efficient compressor chiller setup.

Just throwing an idea at you. I agree that excessive heat is bad for batteries and those battle born guys are not cheap batteries, IMHO cooling them would be worth it.

David

Thanks David.
I have a fair knowledge of refrigerants as I used to work on automotive A/C systems. Still have my EPA card to buy R12, and my vacuum pump and gauges.No R12 left but I still have R134a and some R410-A from when I installed my mini split. I'll check and see what gas my old water cooler uses.
Going to be an interesting project. I'll document it if anyone's interested.

[J.P.M.]

Not fond of the submerge in water idea. Saw too many old movies showing an electrical appliance kicked into a bathtub with the obvious end result.
But your tongue in cheek idea of a fridge got me thinking.
Around here we have no shortage of old inefficient and non working chest freezers big enough to hold half a cow being hauled to the local dump. So to start there's a nice big pre insulated sealed box with a lid. Then replace the old compressor with either a Danfoss 12 volt scroll or a small 120v compressor with it's own pure sine inverter (I have an old water cooler that leaks, so there's my donor compressor, and coils). Lead acid would need a venting system, possibly an Arduino controlled fan and triggered by a hydrogen sensor. The Arduino could also be used for the compressor control to keep the temperatures within a precise set range.
Thank you for planting the seed of an idea.

No disrespect intended here, but unless you're doing this for fun and educational value, even though they're probably not very efficient, I'd get a working fridge. In all likelihood, even if it's C.O.P. and efficiency sucks, unless you know as much about HVAC and refrigeration as you do about law enforcement, it'll most likely still be way more efficient and reliable than what you suggest. Most DIY stuff is simply not efficient or even safe.

Whatever you do, I respectfully suggest you carefully consider ventilation and other safety requirements in anything you come up with.

[citabria]

I am in Silver City, NM with a local elevation of about 7,000 ft msl. I have 12 each-Trojan L16's, on my solar system. June is typically the hottest month, though this year not so much (mid 80's F in the day, and high 40's F at night). I keep the batteries in an unheated outbuilding with morning shading by the Juniper trees.. The batteries sit on a concrete pad. I wrapped the sides and top with blue-board insulation, keeps them at about 53 F in the winter time. In May I open up the blueboard to allow the batteries to cool. In June of 2018, I was a little late in unwrapping the batteries, and they saw about 104 F in the day time for about just two or three days. I have never seen the batteries above 95 F when air is allowed to circulate around them.

So where am I headed with this...as long as your batteries are shaded, and you have some air circulation, the temperature may not be an issue. I suppose the rate of charging may be a factor on the heat generated...

[J.P.M.]

I am in Silver City, NM with a local elevation of about 7,000 ft msl. I have 12 each-Trojan L16's, on my solar system. June is typically the hottest month, though this year not so much (mid 80's F in the day, and high 40's F at night). I keep the batteries in an unheated outbuilding with morning shading by the Juniper trees.. The batteries sit on a concrete pad. I wrapped the sides and top with blue-board insulation, keeps them at about 53 F in the winter time. In May I open up the blueboard to allow the batteries to cool. In June of 2018, I was a little late in unwrapping the batteries, and they saw about 104 F in the day time for about just two or three days. I have never seen the batteries above 95 F when air is allowed to circulate around them.

So where am I headed with this...as long as your batteries are shaded, and you have some air circulation, the temperature may not be an issue. I suppose the rate of charging may be a factor on the heat generated...

Probably sound and common sense advice. At least for starters, keep'em in the shade and they'll probably stay within a few deg. of the ambient temp.

[Selinwine]

I cannot wait to see the final result! I am still learning stuff about cooling and this forum is really helpful. I would love to have some friends that are working in this field, but I don't have any, unfortunately. Luckily, we are living in the era of the internet and everything can be learned here. Now, since everything is closed, I have managed to learn about aircon chemical cleaning and I cannot wait to see its application in real life. That's the beauty related to engineering. Everything can be applied in real life

[robbyg]

I cannot see how actively cooling batteries with a fridge can be a worthwhile unless its a fridge system with a DC compressor system and can be run by some separate panels.